Problem: $ { \left[\begin{array}{rr}{2} & {1} \\ {1} & {-1}\end{array}\right]+\left[\begin{array}{rr}{3} & {1} \\ {-2} & {4}\end{array}\right] = {?} } $
Answer: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{2}+{3} & {1}+{1} \\ {1}+{-2} & {-1}+{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{5} & {2} \\ {-1} & {3}\end{array}\right]}$